JPH0638003B2 - Heat exchanger for water heater - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a heat exchanger for a domestic or commercial hot water heater.

2. Description of the Related Art In a conventional heat exchanger for a water heater, a fin tube heat exchanger and a cylindrical drum are positioned around the heat exchanger to form a combustion chamber, and a heat exchange tube is wound around the drum to form a material. Often uses copper. The heated water receives heat from the heat exchange tube and the fin tube heat exchanger around the drum and is used as hot water.

Problems to be Solved by the Invention In such a heat exchanger, the burner is located at the inlet of the combustion chamber, and the combustion heat of the flame formed on the burner is used. If the hot water is stopped when it is coming out, the temperature of the hot water remaining in the heat exchanger will continue to rise. This phenomenon is generally called post-boiling, and it is considered that the heat of combustion stored in the heat exchanger increased the water temperature. After this, when the user uses hot water again, high-temperature hot water comes out first, which causes burns, which is a safety issue.

On the other hand, a method of forming a cylindrical drum with ceramics has been adopted. This is intended to reduce the size and durability of the heat exchanger. However, combustion heat is stored in this ceramic plate, and this heat heats the water in the fin tube even after the burner is extinguished, and the above-mentioned drawbacks cannot be eliminated.

The present invention reduces the heat storage of the drum and prevents the after-boiling phenomenon.

Means for Solving the Problems And technical means of the present invention for solving the above problems,
Air-permeable ceramics having a honeycomb structure are used for the drum of the heat exchanger, cells constituting the honeycomb are positioned in an appropriate direction, and the surfaces of the ceramics are made dense to eliminate air permeability. The upstream side of the honeycomb is open to the outside air so that cooling air can flow in.

Part of the heat generated from the flame burned in the working burner is radiant, and part of it is supplied to the drum by heat transfer of combustion gas. And most of the heat is supplied to the fin tube heat exchanger. At this time, the heat supplied to the drum heats the air in the honeycomb portion of the drum. Therefore, the air flows upward due to buoyancy and takes away the heat of the ceramics. At this time, since the surface of the ceramic is dense, the air flow inside the drum and the air flow outside are cut off, and the loss of heat to the outside is small. In addition, the buoyancy effect of air in the drum is large and the temperature rise of the drum is small.

Therefore, the amount of heat stored in the drum is small, and it becomes easy to prevent the above-mentioned post-boiling phenomenon.

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, 1 is a heat exchanger body, 2 is a fin tube heat exchanger, 3 is a cylindrical drum, and 4 is a burner for heating the heat exchanger body 1. The heat exchanger body 1 is composed of a fin tube heat exchanger 2 and a drum 3 and constitutes a combustion chamber 5.

The fin-tube heat exchanger 2 is composed of a large number of flat fins 6 and water pipes 7 arranged in a meandering pattern orthogonal to the fins 6. Heating water 8 flows through the water pipes 7 and is generated on the burner 4. It is heated by the high temperature combustion gas 9 and used as hot water.

FIG. 2 is an assembly view of the heat exchanger body 1 and the burner 4, and corresponds to the AA cross section of FIG. 10 is a flame. 11
Is part of the exterior.

FIG. 3 is a detailed view of a part of the drum 3. The material of the drum 3 is ceramics, and the honeycomb structure 12 is formed. As an example, the honeycomb structure is manufactured as follows. A corrugated sheet is formed by adhering the corrugated sheet 13 and the plate-shaped sheet 14, and a large number of cells 16 are formed by using the walls of each sheet as cell walls 15 to form a honeycomb structure. Cooling air 17 passes through the cells.

The cell 16 of the drum 3 includes a corrugated sheet 13 and a plate-shaped sheet 14.
And the cell 16 is located between the beginning 18 and the end 19 of the combustion chamber. The inner surface 20 of the drum 3 is open to the combustion chamber 5, and the outer surface 21 is open to the atmosphere. The ceramics are mainly composed of alumina fiber, and are formed into corrugations by corrugated sheets and plate-shaped sheets. A slurry in which ceramic powder is suspended in water is applied to the surface of this molded product, which is fired in air at 1250 ° C.
The surface of this molded product is dense and has no air permeability, and the porosity after firing is 40 to 95%.

Next, the operation of the structure of this embodiment will be described. The combustion gas supplied to the burner 4 forms a flame 10 on the burner and becomes a high temperature combustion gas 9 which is supplied to the fin tube heat exchanger 2 to heat the heated water 8 and used as hot water. Part of the heat generated by the burner is supplied as radiation, and the other part is supplied to the drum 3 by heat transfer of high-temperature combustion gas. This heat heats the cooling air 17 in the cells 16 of the honeycomb structure. The cooling air gains buoyancy and rises. Therefore, since the heat supplied to the drum 3 is carried away by the cooling air, the heat storage amount of the drum is small.

Heat is supplied to the inner surface 20 of the drum from a flame or hot combustion gases. Since the surface is dense, there is no heat transfer due to gas inflow or outflow such as molecular diffusion. Most heat transfer is due to radiation. Then, this heat is transferred to the corrugated sheet 13.

At this time, the cooling air takes heat from the plate-shaped sheet 14 and the corrugated sheet 13, but the corrugated sheet has a large surface area. Therefore,
The amount of heat carried away by the cooling air 17 passing through the cells 16 is large. Further, since the cell wall around the cell 16 is made of a ceramic heat insulating material, the buoyancy of the cooling air is fully utilized. Since the porosity of the sheet is large, cooling air flows inside the ceramic sheet. As a result, the temperature rise on the outer drum surface 21 is small.

Further, since the drum 3 is the honeycomb structure 12 and the surface thereof is dense, the structural strength is great.

In FIG. 2, the outlet 19 of the drum 3 is located in the fin tube heat exchanger 2, and when the combustion gas passes, the cooling air 17 is blown in and at the same time, the heated cooling air is transferred to the fin tube heat exchanger. The heat is absorbed by the exchanger 2. The cooling air 17 receives buoyancy in the cell 16 and is sucked by the fin tube heat exchanger, so that the flow velocity in the cell is increased, heat can be sufficiently taken by the cell, and the temperature of the outer surface is low.

Further, since the outer surface of the drum is low, the distance from the exterior 11 can be reduced, and the water heater can be easily made small.

Next, another embodiment of the present invention will be described.

FIG. 4 shows another embodiment in which the outlet 22 of the drum of this embodiment is located outside the fin tube heat exchanger 23. With such a structure, the cooling air 26 passing through the cells 25 of the drum 24 is released to the atmosphere from the drum outlet 22. Therefore, it is possible to further prevent the post-boil when the burner and the heated water are stopped.

EFFECTS OF THE INVENTION The present invention forms a honeycomb structure made of a ceramic material in the drum part of a heat exchanger for a water heater, the surface of the drum part is dense and has no air permeability, and the inside has air permeability, and the honeycomb structure The cell is located in the direction of the combustion gas, and the following effects can be obtained.

(1) The heat received from the burner is reduced, and the cooling air passes through the voids of the drum consisting of a honeycomb structure with a small heat capacity, and the heat of the drum is taken away. After boiling can be prevented.

(2) Since it is a honeycomb structure having a high air permeability and a dense surface, it is lightweight and can sufficiently maintain mechanical strength.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of an embodiment of a heat exchanger for a water heater of the present invention, FIG. 2 is a longitudinal sectional view of the same, and FIG. 3 is a perspective view of essential parts constituting a wall of the drum, and FIG. [Fig. 6] is a vertical sectional view of another embodiment. 1 ... Heat exchanger body, 2 ... Fin tube heat exchanger,
3 ... drum, 4 ... burner, 16 ... cell.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Norio Kawabata 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP 60-178213 (JP, A) 23046 (JP, U)

Claims (2)

[Claims] 1. A heat exchanger for a water heater, comprising a drum and a fin tube heat exchanger to form a combustion chamber, wherein the drum is made of a honeycomb structure made of porous ceramics having a plurality of cells, and each cell is A heat exchanger for a water heater characterized in that the surface of the porous ceramics forming the drum, which is positioned in the direction of the combustion gas flow of the heat exchanger, has a dense structure. 2. The porosity of porous ceramics is from 40% to 40%.
The heat exchanger for a water heater according to claim 1, wherein the heat exchanger is 95% and the surface is a thin layer having no air permeability.